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### Topic: charging my acid battery (Read 1 time)previous topic - next topic

#### ardutry

##### Jul 09, 2015, 06:04 am
Hi,
I got an electrolyte (Acid) battery of 12v@7.2AH for a new project I will have with my Arduino, where I'd use 12v dc motors.

Can I charge this battery with my dc adapter with these parameters:

output: 12v@1A

#### mauried

#1
##### Jul 09, 2015, 06:09 am
It depends entirely on the DC adapter and whether its a regulated output adapter with output of 12V, or whether its an unregulated output and the output voltage drops to 12V with a load of 1A.
If its the first type then it wont be useful for charging the battery as the battery will never be fully charged.
If its the 2nd then you need to measure the open circuit voltage and as long as it doesnt go above 14.4 V it will be OK.

#### Wawa

#2
##### Jul 09, 2015, 07:47 am
The voltage of a lead/acid battery, without load, varies between ~12volt (empty) and ~12.8volt (full).

If you use a 12volt supply, it won't charge your battery, because the charging voltage has to be higher than the battery voltage.

Charge current for sealed lead/acid batteries is usually limited to ~1/10 of the Ahr rating of the battery.
The charging voltage for those batteries is usually set to 13.4-13.5volt (float).
Charging time depends on the battery. Age, temperature, etc.
You could measure the charging current. If that drops to almost zero, your battery is full.
That is usually overnight.
Leo..

#### DrAzzy

#3
##### Jul 09, 2015, 09:23 am
Do not simply connect a power adapter directly to a battery, unless it is made for charging a battery.

You need at least some simple electronics to limit current - ideally a charging controller, but it can be as simple as a resistor to limit charge current.

You need more than 12v to charge a 12v battery, as others have noted. A DC-DC converter (they're cheap on ebay) could be used to step up voltage from a readily available one like 12v to the proper voltage for charging , and if you got one with current limiting, it would do that for you too ;-) That's what I did in my 150W flashlights.
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

#### ardutry

#4
##### Jul 09, 2015, 08:13 pmLast Edit: Jul 09, 2015, 08:20 pm by ardutry
Thank you every body for all information,

So in summary:

1. I must obtain a step-up dc-dc converter, I found this on ebay (hope link stilla live):
2A booster board DC-DC step-up module

2. I must limit the 2A current to 500mA as in the battery specification. But how? Could anyone please give a tutorial link or anyway point me to the right direction please?
Maybe there is also a current limiting device on ebay and I just don't know what it is called?

Edit:
I found such item:
current limiter chip
As I understand, the current limiting fucntion is specified by the R-set resistor that will be implemented in the schema realization of this chip, right? Could I do better, or this is the right choice please?

#### DrAzzy

#5
##### Jul 09, 2015, 08:28 pm
Thank you every body for all information,

So in summary:

1. I must obtain a step-up dc-dc converter, I found this on ebay (hope link stilla live):
2A booster board DC-DC step-up module

2. I must limit the 2A current to 500mA as in the battery specification. But how? Could anyone please give a tutorial link or anyway point me to the right direction please?
Maybe there is also a current limiting device on ebay and I just don't know what it is called?

Edit:
I found such item:
current limiter chip
As I understand, the current limiting fucntion is specified by the R-set resistor that will be implemented in the schema realization of this chip, right? Could I do better, or this is the right choice please?

Why not use a converter like this one:
http://www.ebay.com/itm/DC-Converter-Step-Up-Step-Down-Module-4-35V-to-1-25-25V-constant-current-voltage-/221445398662?pt=LH_DefaultDomain_0&hash=item338f2ca086

That one has a current limit built into it. Crank the current limit all the way down, connect it through multimeter on current setting, and adjust the CC pot until you get the current limit you want. Then remove the load and adjust voltage to maximum voltage you want. A LED will change color when the current drops below a second threshold, set by the third pot, to tell you the charging is done.
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

#### TomGeorge

#6
##### Jul 09, 2015, 11:34 pm
Hi,
What does it show on the side of the battery, it sounds like you have a GEL Cell  Lead Acid battery.
12V 7.2Ah.
If so, google the brand and model number, most manufacturers have charging specs and graphs about their product.

Tom.......

Everything runs on smoke, let the smoke out, it stops running....

#### jack wp

#7
##### Jul 09, 2015, 11:45 pm
A 12 volt led acid battery is what is found in most automobiles.
You can give a hefty charge at first (about 14.8 volts) then reduce it to a maintain voltage (about 13.5 volts).
It is possible to let your processor do all this for you (a bit of code and hardware).

#### Wawa

#8
##### Jul 10, 2015, 12:30 am
There are some important differences between a "flooded cell" car battery and the SLA battery mentioned here.

Gel batteries loose their liquid when charged to fast or when you leave them on a too high float/trickle voltage.
And you can't "top up" a gel battery.
Leo..

#### michinyon

#9
##### Jul 10, 2015, 02:40 am
Quote
So in summary:
unless you are planning to experiment,  it might be easier to get a device made for the job,  such as

http://www.ebay.com/itm/Car-Truck-Motorcycle-12V-Smart-Compact-Battery-Charger-Tender-Maintainer-NEW-/371150453508?hash=item566a4a7b04&item=371150453508&vxp=mtr

And there are plenty of other examples.

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